Catheter with composite construction

ABSTRACT

A catheter has a composite and segmented construction in a distal section that includes deflectable members and support member arranged in alternating sequence, with each support member carrying a ring electrode and the deflectable members being flexible to allow deflection of the distal section as a whole. Carried on an outer surface of the support member is a coil location sensor. The distal section is configured with a distal irrigation fluid path extending axially through the deflectable members and the support members to deliver irrigation fluid to the ring electrode and the tip electrode. A method of constructing a catheter includes building a section of the catheter from the inside out by mounting the support members on a tubing at predetermined locations and filling gaps in between with a more flexible material to form the deflectable members by extrusion segments or injection molding over assembled components internal to the catheter.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The application is a divisional of and claims priority to and thebenefit of U.S. patent application Ser. No. 15/664,652 filed Jul. 31,2017, now U.S. Pat. No. 10,512,503, which is a divisional of and claimspriority to and the benefit of U.S. patent application Ser. No.13/430,530 filed Mar. 26, 2012, issued as U.S. Pat. No. 9,717,554, theentire contents of all of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to an electrophysiologic catheter that isparticularly useful for ablation and sensing electrical activity ofheart tissue.

BACKGROUND OF INVENTION

Electrode catheters have been in common use in medical practice for manyyears. Diagnosis and treatment of cardiac arrythmias by means ofelectrode catheters include mapping the electrical properties of hearttissue and selectively ablating cardiac tissue by application of energy.Such ablation can cease or modify the propagation of unwanted electricalsignals from one portion of the heart to another. The ablation processdestroys the unwanted electrical pathways by formation of non-conductinglesions. Various energy delivery modalities have been disclosed forforming lesions, and include use of microwave, laser and more commonly,radiofrequency energies to create conduction blocks along the cardiactissue wall.

In a two-step procedure—mapping followed by ablation—electrical activityat locations within the heart is typically sensed and measured byadvancing a catheter containing one or more electrical sensors (orelectrodes) into the heart, and acquiring data at a multiplicity oflocations. These data are then utilized to select the tissue targetareas at which ablation is to be performed.

In use, the electrode catheter is inserted into a major vein or artery,e.g., the femoral artery, and then guided into the chamber of the heartwhich is of concern. A reference electrode is provided, generally tapedto the patient's skin or provided on the ablation catheter or anothercatheter. Radio frequency (RF) current is applied to the ablationelectrode of the catheter, and flows through the surrounding media,i.e., blood and tissue, toward the reference electrode. The distributionof current depends on the amount of electrode surface in contact withthe tissue, as compared to blood which has a higher conductivity thanthe tissue.

Heating of the tissue occurs due to its electrical resistivity. Thetissue is heated sufficiently to cause cellular destruction in thecardiac tissue resulting in formation of a lesion within the cardiactissue which is electrically non-conductive. During this process,heating of the ablation electrode also occurs as a result of conductionfrom the heated tissue to the electrode itself. If the electrodetemperature becomes sufficiently high, possibly above 60° C., a thintransparent coating of dehydrated blood can form on the surface of theelectrode. If the temperature continues to rise, this dehydrated layerof blood can become progressively thicker resulting in blood coagulationon the electrode surface. Because dehydrated biological material has ahigher electrical resistance than tissue, impedance to the flow ofelectrical energy into the tissue also increases. If the impedanceincreases sufficiently, an impedance rise occurs and the catheter mustbe removed from the body and the tip electrode cleaned.

In a typical application of RF current, circulating blood provides somecooling of the ablation electrode. Another method is to irrigate theablation electrode, e.g., with physiologic saline at room temperature,to actively cool the ablation electrode instead of relying on the morepassive physiological cooling provided by the blood. Because thestrength of the RF current is no longer limited by the interfacetemperature, current can be increased. This results in lesions whichtend to be larger and more spherical, usually measuring about 10 to 12mm.

The clinical effectiveness of irrigating the ablation electrode isdependent upon the distribution of flow within the electrode structureand the rate of irrigation flow through the catheter. Effectiveness isachieved by reducing the overall electrode temperature and eliminatinghot spots in the ablation electrode which can initiate coagulumformation. More channels and higher flows are more effective in reducingoverall temperature and temperature variations, i.e., hot spots. Thecoolant flow rate must be balanced against the amount of fluid that canbe injected into the patient and the increased clinical load required tomonitor and possibly refill the injection devices during a procedure. Inaddition to irrigation flow during ablation, a maintenance flow,typically a lower flow rate, is required throughout the procedure toprevent backflow of blood into the coolant passages. Thus, reducingcoolant flow by utilizing it as efficiently as possible is a desirabledesign objective.

Another consideration is the ability to control the exact position andorientation of the catheter tip. This is ability is critical and largelydetermines the usefulness of the catheter. It is generally known toincorporate into electrophysiology catheters an electromagnetic (EM)tri-axis location/position sensor for determining the location of acatheter's distal end. An EM sensor in the catheter, typically near thecatheter's distal end within the distal tip, gives rise to signals thatare used to determine the position of the device relative to a frame ofreference that is fixed either externally to the body or to the heartitself. The EM sensor may be active or passive and may operate bygenerating or receiving electrical, magnetic or ultrasonic energy fieldsor other suitable forms of energy known in the art.

U.S. Pat. No. 5,391,199, the entire disclosure of which is incorporatedherein by reference, describes a position-responsive catheter comprisinga miniature sensor coil contained in the catheter's distal end. The coilgenerates electrical signals in response to externally-applied magneticfields, which are produced by field-generator coils placed outside thepatient's body. The electrical signals are analyzed to determinethree-dimensional coordinates of the coil.

U.S. Pat. No. 6,690,963, the entire disclosure of which is herebyincorporated by reference, is directed to a locating system fordetermining the location and orientation of an invasive medicalinstrument, for example a catheter or endoscope, relative to a referenceframe, comprising: a plurality of field generators which generate known,distinguishable fields, preferably continuous AC magnetic fields, inresponse to drive signals; a plurality of sensors situated in theinvasive medical instrument proximate the distal end thereof whichgenerate sensor signals in response to said fields; and a signalprocessor which has an input for a plurality of signals corresponding tosaid drive signals and said sensor signals and which produces the threelocation coordinates and three orientation coordinates of a point on theinvasive medical instrument.

Because of the size of the tip electrode and the limited interior spacetherein, the EM sensor is often positioned outside of the tip electrode,proximally thereof, and often off-axis from the tip electrode which canreduce the accuracy of the position sensing capabilities of the sensor.Being outside the tip electrode, the position sensor is also exposed tobending stresses and can limit the flexibility and deflection of thedistal tip section. Moreover, the sensor can be damaged by RF energyduring ablation.

Where the distal tip is irrigated, the efficiency of irrigated coolingbecomes a significant factor as ablation procedures can last five or sixhours resulting in extensive fluid-loading in the patient. Conventionalirrigated tip electrodes typically operate with a flow rate of about 17ml/minute at below about 30 watts of RF ablation energy to about 30-50ml/minute at about 30 watts or greater.

Current catheters include irrigated ring electrodes that are adapted forablation. Such catheters include coil or single axis sensors (SASs) forvisualization of the irrigated ring electrodes. However, the sensors aretypically housed in a dedicated lumen of a multi-lumened tubingtypically used with deflectable catheters. As lumens are needed forother components, such as puller wires, lead wires, and/or irrigationtubing, it becomes difficult to maintain typical catheter sizes. Ascatheters become more complex, more components are incorporated and thusthe allocation of space for each component becomes more challenging.

Accordingly, it is desirable that a catheter be adapted for mapping andablation with improved cooling and position sensing characteristics byproviding a tip section that carries irrigated tip and ring electrodesand their location sensors in a manner that minimizes the increase insize of the tip section without interfering with the functionality ofthe components carried therein.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter having a composite andsegmented construction in a distal section that allows space in thedistal section to be used efficiently without the need to increasecatheter size. The distal section includes at least one deflectablemember and at least one support member arranged in alternating sequence,with the support member being sufficiently rigid to support and carry aring electrode and the deflectable member being more flexible than thesupport member to allow deflection of the distal section as a whole.Also carried on the support member for the ring electrode is a locationsensor, e.g., a single axis coil sensor. The sensor is carried on anouter surface of the support member so that lumens within the supportmember can be used for other components such as lead wires, thermocouplewires, puller wires, irrigation fluid, and/or sensor cable whichtypically occupy less space than a location sensor. The distal sectionis also configured with a distal irrigation fluid path extending axiallythrough the deflectable member and the support member to deliverirrigation fluid to the ring electrode and the tip electrode.

In an embodiment of the present invention, a catheter has an elongatedcatheter body, and a distal section with a composite construction havingalternating segments of deflectable members and support members whereeach support member carries a respective irrigated ring electrode, and asingle axis location coil sensor that is wound on an outer surface ofthe support member. The coil sensor is situated between the ringelectrode and the support member but isolated from irrigation fluidpassing through a reservoir formed between the ring electrode and thesupport member. In that regard, a distal irrigation tube extends throughthe length of the distal section to provide a fluid path that deliversirrigation fluid to the ring electrodes and the tip electrode.

In an embodiment, the tip electrode has a shell wall that defines acavity through which fluid flows and exits via fluid ports formed in theshell wall. The cavity is sealed by an internal member that extends intothe cavity to safely house a position sensor for the tip electrode. Aproximal portion of the internal member disperses fluid entering the tipelectrode for a more uniform flow through the cavity. As such, fluid isfed to the more distal fluid ports in the tip electrode for more uniformcooling at all locations on the tip electrode.

The present invention is also directed to a method of constructing acatheter. The method includes building a section of the catheter fromthe inside out by providing a tubing, a plurality of support members,and an irrigated ring electrode for each support member. The methodincludes mounting the support members on the tubing at predeterminedlocations by inserting the tubing through a lumen of each support memberand separating adjacent support members on the tubing by a predeterminedspacing. The method further includes mounting an irrigated ringelectrode on each support member. The method also includes formingdeflectable member on the tubing to fill in the predetermined spacingand connect adjacent support members with a material less rigid than theconstruction material of the support members. The deflectable membersmay be cut from extrusions, or may be injection molded over assembledcomponents internal to the catheter. The support members may befabricated using micro machining, micro molding, or machining ofextrusions using plastic materials which are sufficiently rigid tosupport a ring electrode and sufficiently biocompatible for contact withblood. The deflectable member and the support members may bemulti-lumened to accommodate lead wires, puller wires, thermocouplewires, sensor cables and/or irrigation fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective of a catheter according to an embodiment of thepresent invention.

FIG. 2A is a side cross-sectional view of the catheter FIG. 1, showing ajunction between a catheter body and a deflectable intermediate section,taken along a first diameter.

FIG. 2B is a side cross-sectional view of the catheter of FIG. 1,showing a junction between a catheter body and a deflectableintermediate section, taken a long a second diameter generallyperpendicular to the first diameter.

FIG. 2C is a longitudinal cross-section view of the deflectableintermediate section of FIG. 2B taken along line C-C.

FIG. 3 is a perspective view of a distal section of the catheter of FIG.1, with components broken away to show the interior.

FIG. 3A is a side cross-sectional view of the distal section of FIG. 3,including a distal-most ring electrode and support member, taken along afirst diameter.

FIG. 3B is a side cross-sectional view of the distal section of FIG. 3,including a distal-most ring electrode and support member, taken along asecond diameter, generally perpendicular to the first diameter.

FIG. 3C is a side cross-sectional view of the distal section of FIG. 3,including a distal-most ring electrode and support member, taken along athird diameter between the first and second diameters.

FIG. 3D is an end cross-sectional view of the distal section of FIG. 3,taken along line D-D

FIG. 3E is an end cross-sectional view of the distal section of FIG. 3,taken along line E-E.

FIG. 4 is a perspective view of an embodiment of a ring electrode.

FIG. 5 is a side cross-sectional view of the tip electrode of FIG. 3.

FIG. 5A is an end cross-sectional view of the tip electrode of FIG. 5,taken along line A-A.

FIG. 5B is an end cross-sectional view of the tip electrode of FIG. 5,taken along line B-B.

FIG. 5C is an end cross-sectional view of the tip electrode of FIG. 5,taken along line C-C.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an embodiment of a catheter 10 carrying irrigated tipand ring electrodes with location sensing and cooling capabilities. Thecatheter has an elongated catheter body 12 with proximal and distalends, an intermediate deflectable section 14 at the distal end of thecatheter body 12, and a distal section 15 with an irrigated tipelectrode 17 and a plurality of irrigated ring electrodes 21. Thecatheter also includes a control handle 16 at the proximal end of thecatheter body 12 for controlling deflection of the intermediate section14. Advantageously, the distal section 15 has a composite and segmentedconstruction comprising alternating segments of deflectable lumenmembers 54 and ring electrode support members 56. The constructionfacilitates the efficient use of space in the distal section 15 as theconstruction allows all the lumens in the distal section to be used forcomponents other than position sensing coils which otherwise tend torequire dedicated and larger lumens.

With reference to FIGS. 2A and 2B, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an imbedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate puller members(e.g., puller wires), lead wires, and any other desired wires, cables ortubings. If desired, the inner surface of the outer wall 20 is linedwith a stiffening tube 22 to provide improved torsional stability. Adisclosed embodiment, the catheter has an outer wall 20 with an outerdiameter of from about 0.090 inch to about 0.94 inch and an innerdiameter of from about 0.061 inch to about 0.065 inch.

Distal ends of the stiffening tube 22 and the outer wall 20 are fixedlyattached near the distal end of the catheter body 12 by forming a gluejoint 23 with polyurethane glue or the like. A second glue joint (notshown) is formed between proximal ends of the stiffening tube 20 andouter wall 22 using a slower drying but stronger glue, e.g.,polyurethane.

Components that extend between the control handle 16 and the deflectablesection 14 pass through the central lumen 18 of the catheter body 12.These components include lead wires 40 for the tip electrode 17 and ringelectrodes 21 on the distal section 15, an irrigation tubing 38 fordelivering fluid to the distal section 15, cables 48 forposition/location sensors 46 located in the tip electrode and the ringelectrodes, a pair of puller wires 26 for bi-directional deflection ofat least the intermediate section 14 if not also the distal section 15,and a pair of thermocouple wires 41, 45 to sense temperature at thedistal section 15.

Illustrated in FIGS. 2A, 2B and 2C is an embodiment of the intermediatesection 14 which comprises a short section of tubing 19. The tubing alsohas a braided mesh construction but with multiple off-axis lumens, forexample five lumens 31, 32, 33, 34 and 35. Each of off-axis,diametrically opposing first and second lumens 31, 32 carries a pullerwire 26. A third off-axis lumen 33 carries the lead wires 40 and thethermocouple wires 41 and 45. A fourth off-axis lumen 34 carries thesensor cables 48. A fifth center lumen 35 carries the irrigation tubing38.

The tubing 19 of the intermediate section 14 is made of a suitablenon-toxic material that is more flexible than the catheter body 12. Asuitable material for the tubing 19 is braided polyurethane, i.e.,polyurethane with an embedded mesh of braided stainless steel or thelike. The size of each lumen is not critical, but is sufficient to housethe respective components extending therethrough.

A means for attaching the catheter body 12 to the intermediate section14 is illustrated in FIGS. 2A and 2B. The proximal end of theintermediate section 14 comprises an outer circumferential notch 24 thatreceives an inner surface of the outer wall 20 of the catheter body 12.The intermediate section 14 and catheter body 12 are attached by glue orthe like.

If desired, a spacer (not shown) can be located within the catheter bodybetween the distal end of the stiffening tube (if provided) and theproximal end of the intermediate section. The spacer provides atransition in flexibility at the junction of the catheter body andintermediate section, which allows this junction to bend smoothlywithout folding or kinking. A catheter having such a spacer is describedin U.S. Pat. No. 5,964,757, the disclosure of which is incorporatedherein by reference.

Each puller wire 26 is preferably coated with Teflon®. The puller wires26 can be made of any suitable metal, such as stainless steel or Nitinoland the Teflon coating imparts lubricity to the puller wire. The pullerwire preferably has a diameter ranging from about 0.006 to about 0.010inch.

As shown in FIG. 2B, a portion of each puller wire 26 extending throughthe catheter body 12 passes through a compression coil 37 in surroundingrelation to its puller wire 26. The compression coil 37 extends fromabout the proximal end of the catheter body 12 to about the proximal endof the intermediate section 14. The compression coil 37 is made of anysuitable metal, preferably stainless steel, and is tightly wound onitself to provide flexibility, i.e., bending, but to resist compression.The inner diameter of the compression coil is preferably slightly largerthan the diameter of the puller wire 26. Within the catheter body 12,the outer surface of the compression coil 37 is also covered by aflexible, non-conductive sheath 39 (FIG. 2B), e.g., made of polyimidetubing. As shown in FIGS. 2B and 2C, a portion of each puller wire 26extending through the intermediate section 14 is covered by anonconductive protective sheath 47.

Proximal ends of the puller wires 26 are anchored in the control handle16. In the disclosed embodiment, distal ends of the puller wires 26 areanchored in the distal section 15 as described further below. Separateand independent longitudinal movement of the puller wire 26 relative tothe catheter body 12 which results in deflection of the intermediatesection 14 and tip section 15 is accomplished by suitable manipulationof the control handle 16.

In the illustrated embodiment of FIG. 1, the control handle 16 has adeflection actuator 50 that actuates the puller wires for bi-directionaldeflection. The control handle also includes a deflection tension knob52 that enables the user to adjust the ease by which the deflectionactuator can be rotated. A suitable deflection assembly and controlhandle are described in co-pending U.S. application Ser. No. 12/346,834,filed Dec. 30, 2008, entitled DEFLECTABLE SHEATH INTRODUCER, the entiredisclosure of which is hereby incorporated by reference. Other suitabledeflection assemblies are described in co-pending U.S. application Ser.No. 12/211,728, filed Sep. 16, 2008, entitled CATHETER WITH ADJUSTABLEDEFLECTION SENSITIVITY, and U.S. application Ser. No. 12/127,704, filedMay 27, 2008, entitled STEERING MECHANISM FOR BI-DIRECTIONAL CATHETER,the entire disclosures of both of which are hereby incorporated byreference.

With reference to FIG. 3, at the distal end of the intermediate section14 is the distal section 15 that includes the tip electrode 17 and aplurality of irrigated ring electrodes 21. The distal section has acomposite construction that includes alternating segments of deflectablelumen members 54 and ring electrode support members 56. In theillustrated embodiment, the composite construction includes a firstdeflectable lumen member 54 a that is immediately distal of the distalend of the intermediate section 14, and a first support member 56 a isimmediately distal of the first deflectable lumen member 54 a. Withthree ring electrodes 21 in the illustrated embodiment, the distalsection 15 includes three deflectable lumen members 54 a, 54 b, 54 c andthree support members 56 a, 56 b, 56 c, arranged in an alternatingsequence along the distal section 15, with each ring electrode 21 beingmounted on a respective support member 56. It is understood that thepresent invention includes any combination/plurality of deflectablelumen members 54 and support members 56. Depending on the embodiment,there may be a greater plurality of members 54 than members 56,including N plurality of members 54 and N+1 plurality of members 56, orvice versa, or the same plurality of members 54 and 56.

The ring electrode support members 56 may be constructed of asufficiently rigid plastic material suitable for housingposition/location sensors, such as SASs, to regulate irrigation flow toirrigated ring electrodes 21 and to act as a substrate on which the ringelectrode 21 is mounted. Each support member 56 has a similarconstruction with a plurality of lumens 71, 72, 73, 74. 75 thatpreferably are in axial alignment with the lumens 61, 62, 63, 64, 65,respectively of the deflectable lumen members 54. In the illustratedembodiment of FIGS. 3A, 3B and 3E, each member 56 includes first andsecond diametrically-opposed, off axis lumens 71, 72, each for arespective puller wire 26, a third off-axis lumen 73 for electrode leadwires 40 and thermocouple wires 41, 45, a fourth off-axis lumen 74 forsensor cables 48, and a fifth center lumen 75 for irrigation fluid. Thelength of each support member 56 can range between about 0.2 cm and 1.0cm, and preferably about 0.5 cm. It is understood that the length of themembers 56 may or may not be generally equal to the length of themembers 54, as desired or appropriate.

The support members 56 may be fabricated using micro machining, micromolding, or machining of extrusions using plastic materials which aresufficiently rigid and sufficiently biocompatible for contact withblood.

Extending between adjacent support members 56 are the deflectable lumenmembers 54 which are more flexible and less rigid than the supportmembers 56 so as to allow for the distal section 15 to bend and deflectwhen tension is applied to the puller wires 26. Each deflectable lumenmember 54 has a similar construction with a plurality of lumens 61, 62,63, 64, 65. In the illustrated embodiment of FIGS. 3A, 3B and 3D, themember 54 includes first and second diametrically-opposed, off-axislumens 61, 62, each for a respective puller wire 26, a third off-axislumen 63 for electrode lead wires 40 and thermocouple wires 41, 45, afourth off-axis lumen 64 for sensor cables 48, and a fifth center lumen65 for irrigation fluid.

The length of each deflectable lumen member 54 can range between about0.2 cm and 2.0 cm, and preferably about 0.5 cm. The deflectable lumenmembers 54 are constructed of a flexible biocompatible material,including flexible polymers and thermoplastic elastomers, such asPELLETHANE or PEBAX. Each deflectable lumen member 54 may be cut fromextrusions or may be injection molded over assembled components internalto the catheter such as an irrigation fluid tubing, lead wires, sensorcables and puller wires.

Ends of the deflectable lumen members 54 and the support members 56 maybe joined by in any suitable manner, including adhesives, thermalbonding, sonic bonding or over-molding. The lumens 61-65 of thedeflectable lumen members 54 and the lumens 71-75 of the support members56 are aligned so that the puller wires 26, lead wires 40, thermocouplewires 41 and 45, and sensor cables 48 can extend through the distalsection 15 without sharp bends or kinks.

It is understood that the lumens 65 of the deflectable lumen members 54and the lumens 75 of the support members 56 may receive a singlecontinuous distal irrigation tubing 79 that lines the lumens 65 and 75to provide a distal irrigation fluid path through the distal section 15.

According to a feature of the present invention, a circumferentialgroove 80 is formed in the outer surface of each support member 56. Inthe illustrated embodiment of FIGS. 3A and 3B, the groove 80 is formednear a proximal end of the support member 56, although it is understoodthat the groove 80 may be formed near a distal end of the support member56. The groove 80 is provided on the support member 56 to carry a wirecoil of a sensor 36R for each irrigated ring electrode 21. The wire coil(e.g., a single-axis sensor “SAS”) is advantageously wound in the groove80 on the support member 56 so that it does not occupy any space in thedistal section 15 beyond that already occupied by the support member 56.Moreover, the wire coil does not occupy any lumens of the support member56. Rather, the lumens are available to other components, including leadwires, thermocouple wires and puller wires, that do not necessarilyrequire dedicated lumens and/or larger lumens as a typical sensor would.

The sensor cables 48 connected to each end of the coil 36R extendthrough the fourth lumen 74 of the support member 56. A passage 82 (FIG.3A) through the support member 56 allowing communication between thelumen 74 and the groove 80 is provided at each end of the groove. Onesensor cable 48 is fed through a respective passage 82 for connection toeach end of the wire coil of the sensor 36R, so each sensor 36R has apair of cables connected to it.

The irrigated ring electrodes 21 are adapted for ablation and irrigationand have a similar structure. The ring electrodes may be made of anysuitable noble metal, such as platinum or gold, preferably a combinationof platinum and iridium or gold and platinum. In the illustratedembodiment, the ring electrode 21 is generally cylindrical with a lengthgreater than its diameter. With reference to FIG. 4, the ring electrodehas a distal end 90, a mid-section 92 and a proximal end 94. With a wall96 of a generally uniform thickness throughout its length, the ringelectrode 21 has a larger diameter in the mid-section 92 than in thedistal and proximal ends 90, 94. As such, the wall bulges outwardly inthe mid-section with curved transitional regions 98 on each side of themid-section 92 so as to provide the ring electrode with an atraumaticprofile without corners or sharp edges. As illustrated in theembodiments of FIGS. 3A and 3B, a reservoir in the shape of an annulargap G is formed between an inner surface of the mid-section 92 and anouter surface of the support member 56. A plurality of irrigationapertures 100 are formed in the wall 96 of the mid-section 92 to promoteflow in a radial direction, and of the curved transitional regions 98 topromote flow in an axial direction. In the latter instance, theapertures 100 in the curved transitional regions 98 are particularlyeffective in minimizing charring and coagulation which are likely to be“hot spots” resulting from higher current densities due to transitionsin the electrode profile. In that regard, the curved transitionalregions 98 may have more apertures 100 and/or apertures with a greatercross-section so as to minimize the occurrence of hot spots. Othersuitable ring electrodes are described in US Patent ApplicationPublication No. US2010/0168548 A1, and U.S. patent application Ser. No.13/174,742, filed Jun. 30, 2011, the entire content of both of which areincorporated herein by reference.

The ring electrodes 21 can be made of any suitable solid conductivematerial, such as platinum or gold, preferably a combination of platinumand iridium. The ring electrodes can be mounted onto the support members56 with glue or the like. The rings electrodes may be monopolar orbi-polar. In the illustrated embodiment, there are a distal monopolarring electrode and a proximal pair of bi-polar ring electrodes. Eachring electrode is connected to a respective lead wire 40R.

Each lead wire 40R is attached to its corresponding ring electrode 21 byany suitable method. A preferred method for attaching a lead wire to aring electrode involves first making a small hole through the wall ofthe non-conductive covering or tubing. Such a hole can be created, forexample, by inserting a needle through the support member 56 and heatingthe needle sufficiently to form a permanent hole. The lead wire is thendrawn through the hole by using a microhook or the like. The end of thelead wire is then stripped of any coating and welded to the underside ofthe ring electrode, which is then slid into position over the hole andfixed in place with polyurethane glue or the like.

With reference to FIGS. 3C and 3E, openings 77 are formed in the distalirrigation tubing 79 which communicate with passages 76 formed in thesupport member 56 to provide fluid communication between the irrigationlumen 75 and the gap reservoir G of each ring electrode 21. The passages76 are formed at a predetermined radial angle (FIG. 3E) so that thepassages 76 do not interfere with the off-axis lumens in each of thesupport member 56. Advantageously, the passages can be preciselydimensioned so as to regulate the volumetric flow rate of the irrigationfluid delivered to the gap reservoirs G.

The length of a ring electrode 21 is about equal to the length of asupport member 56 so that the support member is covered in its entiretyby its respective ring electrode. The groove 80 and the coil sensor 36Rare positioned under the distal end 90 (or the proximal end 92) of thering electrode 21 so that the coil sensor 36R is not exposed toirrigation fluid in the gap reservoir G of the ring electrode. Thedistal and proximal ends 90 and 94 of the ring electrodes are sizedrelative to the support members 56 so as to form a fluid tight sealenclosing the gap reservoir G.

With reference to FIGS. 3 and 5, distal of the distal-most irrigatedring electrode 21 c is the tip electrode 17 which is connected by aconnection section 81 having a contact force spring 83 and anonconductive cover 85. A proximal end of the the cover 85 and a distalend of the support member 56 c (and ring electrode 21 c) may be joinedby a glue joint 84. The contact force spring 83 may be a coil or spiralform or a tube with radial cuts for allowing relativemovement/deflection between the tip electrode 17 and the distal-mostirrigated ring electrode 21 c when a deflection force is applied to thetip electrode 17, such as when the tip electrode 17 comes in contactwith tissue. Extending longitudinally through the spring 83 is anirrigation connector lumen 86 that extends between the tip electrode 17and the center irrigation lumen 75 of the distal-most irrigated ringelectrode 21 c.

The tip electrode 17 houses an electromagnetic position sensor 36T in adistal and on-axis location relative to the tip electrode. The tipelectrode is configured to promote turbulent flow and dispersion ofirrigation fluid for increased thermal transfer from the tip electrodeto the fluid and thus with lower flow rates resulting in lower fluidload in the patient. Fluid, e.g., saline or heparinized saline, can bedelivered to the ablation site from the tip electrode to cool tissue,reduce coagulation and/or facilitate the formation of deeper lesions. Itis understood that other fluids can be delivered as well, including anydiagnostic and therapeutic fluids, such as neuroinhibitors andneuroexcitors.

The tip electrode 17 has a two-piece configuration that includes anelectrically conductive dome shell 110 and an internal member 112. Theshell 110 is generally cylindrical defining a chamber 113 between aclosed distal end 114 and an open proximal end (or neck) 116. The neck116 connected with a distal end of the nonconductive cover 85 of theconnection section 81. The internal member 112 is configured to fitinside the shell 110 with an elongated distal section 118 that sitsinside the chamber 113, and a proximal core 120 that plugs the neck 116.The core 120 and the distal section 118 are connected by a stem 119. Thedistal end 114 of the shell 110 and the distal section 118 of theinternal member 112 are relatively sized so that the chamber 113functions as a tip reservoir for irrigation fluid entering the tipelectrode 17. Fluid passages 124 are formed in the core 120 to providefluid communication from the irrigation connector lumen 86 to thechamber 113.

The shell 110 is constructed of a biocompatible metal, including abiocompatible metal alloy. A suitable biocompatible metal alloy includesan alloy selected from stainless steel alloys, noble metal alloys and/orcombinations thereof. In one embodiment, the shell is constructed of analloy comprising about 80% palladium and about 20% platinum by weight.In an alternate embodiment, the shell is constructed of an alloycomprising about 90% platinum and about 10% iridium by weight. The shellcan formed by deep-drawing manufacturing process which produces asufficiently thin but sturdy wall that is suitable for handling,transport through the patient's body, and tissue contact during mappingand ablation procedures. A deep drawn shell is also suitable forelectrical discharge machining (EDM) process to form a large pluralityof through-holes or ports 122 in the shell that allow fluidcommunication between the chamber 113 and outside the shell 110.

The elongated distal section 118 of the internal member 112 isconfigured to protect and encapsulate the tip electrode sensor 36T whichis positioned centrally within the chamber 113 so that the sensor isdistal and centered in the tip electrode for optimum performance. In thedisclosed embodiment, the tip electrode sensor 36T is an electromagnetic(EM) tri-axis location/position sensor using three coils that give riseto signals that are used to determine the position of the devicerelative to a frame of reference that is fixed either externally to thebody or to the heart itself. The EM sensor may be active or passive andmay operate by generating or receiving electrical, magnetic orultrasonic energy fields or other suitable forms of energy known in theart.

The core 120 of the internal member 112 sits in the neck 116 of theshell 110. The core is advantageously configured as a diffuser thatprovides multiple fluid passages or channels 124 through the neck 116 soas to diffuse the irrigation fluid. As such, the diffusing core 120provide increased turbulence and a more uniform flow rate in the chamber113 and thus more increased convective cooling on the shell 110.Irrigation in the tip electrode 17 is thus more uniform throughout thelength of the tip electrode. The internal member 112 effectivelycounters the tendency for the velocity of the fluid entering the tipelectrode 17 to otherwise carry the fluid to the more distal ports andstarve the more proximal ports 122.

On a proximal surface of the core 120, a center opening 130 (FIG. 5A)connects a distal end of the connector irrigation lumen 86 with thechannels 124 in the core 120. Within the core 120, the channels 124intersect each other at varying degrees throughout the tip electrode(FIG. 5B), and then separate into distinct channels (FIG. 5C.) In theillustrated embodiment, the channels 124 have a circular cross-section,however, it is understood that the cross-section may be polygonal or anynoncircular shape and can have any suitable size, as appropriate. Thecore 120 is made of electrically conductive material so as to beconductive with the shell 110 when the core 120 is energized by its leadwire 40T, but the distal section 118 can be made of plastic such aspolyimide, or an adhesive or sealant, such as epoxy, to encapsulate thetip electrode sensor 36T.

Also on the proximal surface of the core 120 are blind holes 132, 133(FIG. 5A) for the tip electrode lead wire 40T, the thermocouple wires41, 45. A longitudinal through-hole 134 extending through the core 120,the stem 119 and into the distal section 118 of the internal member 112is provided for the cable 48T for the tip electrode sensor 36T. Thethrough-hole or passage 134 is routed from a proximal off-axis locationin the core 120 to a distal on-axis location in the stem 119 withoutinterfering with the fluid diffusing channels 124.

A distal end of each puller wire 26 has a T-bar 135. In the illustratedembodiment of FIG. 3B, the T-bars are anchored in the first and secondlumens 61, 62 of the distal-most deflectable lumen member 54 c. In thealternative, the distal ends of the puller wires 26 may be soldered indiametrically-opposing off axis blind-holes in the proximal surface ofthe core 120 of the tip electrode 17.

In accordance with another feature of the present invention, fluid isdelivered through the catheter body 12 via the irrigation tubing 38(FIG. 2A), through the intermediate section 14 via the irrigation lumen35 (FIG. 2A), through the distal section 15 via the lumen 65 (FIG. 3A)of the deflectable lumen members 54 and the lumen 75 (FIG. 3A) of thering electrode support members 56. A portion of the fluid enters thereservoir gap G of the ring electrodes via the opening 77 and thepassage 76 (FIG. 3C), and exits the ring electrodes via the apertures100. Another portion of the fluid continues to the tip electrode 17 viaconnector irrigation lumen 86 and the diffusing channels 124 (FIG. 5),where it enters the chamber 113 and exits the tip electrode viairrigation ports 122. In the tip electrode 17, the fluid has a flow thatis more uniform and equal in the radial direction through the diffusingchannels 124 which in turn provides increased turbulence and a moreuniform flow rate in the chamber 113 and thus more increased convectivecooling on the shell 110. Irrigation in the tip electrode is thus moreuniform throughout the length of the tip electrode. Suitable tipelectrodes are described in U.S. patent application Ser. No. 12/767,763,filed Apr. 26, 2010 entitled “IRRIGATED CATHETER WITH INTERNAL POSITIONLOCATION SENSOR,” the entire disclosure of which is incorporated hereinby reference.

The lead wires 40T and 40R pass through the lumens 63 and 73 (FIG. 3A)of the deflectable lumen members 54 and the support members 56, thelumen 33 (FIG. 2A) of the tubing 19 of the deflectable intermediatesection 14 and the central lumen 18 (FIG. 2A) of the catheter body 12.The portion of the lead wires extending through the central lumen 18 ofthe catheter body 12, and proximal portion of the lumen 33 can beenclosed within a protective sheath 67 (FIG. 2A), which can be made ofany suitable material, preferably polyimide. The protective sheath isanchored at its distal end to the proximal end of the intermediatesection 14 by gluing it in the lumen 33 with polyurethane glue or thelike. Each electrode lead wire has its proximal end terminating in aconnector (not shown) at the proximal end of the control handle 16. Thetip electrode 17 and ring electrodes 21 are electrically connected to asource of ablation energy by the lead wires 40T and 40R via theconnector. The wires may also be electrically connected to anappropriate mapping or monitoring system via the connector.

Whereas conventional construction methods build a catheter “from theoutside in,” the present catheter, in particular, the compositeconstruction of the distal section 15, allows for an “inside out”construction in which the section is built up from the inside ratherthan from the outside. As such, the distal section 15 and the cathetercan be built around the distal irrigation tubing 79. The support members56 are placed on the distal irrigation tubing 79 at predeterminedlocations separated by predetermined, generally uniform gaps or spacing.For example, the tubing 79 can be fed through each lumen 75 of thesupport members 56 so that the members 56 are “strung” on the tubing 79.The passage 76 for irrigation in each support member can be formed alongwith or at a different stage from the formation of the irrigationopenings 77 in the tubing 79. The coil sensors 36R are wounded in thegroove 80 on the support members 56 and connected to the cables 48extending through the lumens 74 of the support members 56. The radialirrigation fluid passage 76 is formed in each support member and a ringelectrode 21 is then mounted on each support member. The lead wires 40Rrouted through the lumens 73 of each of the support member 56 areconnected to the ring electrodes 21. The lead wire 40T and thermocouplewires 41 and 45 for the tip electrode 17 are routed through the lumen 73and the puller wires 26 are routed through the lumens 71 and 72 of thesupport members 56. After all of the components are in place to create asub-assembly of the distal section 15, the deflectable lumen members 54are added on to the irrigation tubing 79 to fill in and connect the gapsbetween the support members 56. For example, the sub-assembly can beplaced in a mold for injection with a suitable material (e.g., apolymer) to complete the formation of the deflectable lumen members 54.

The preceding description has been presented with reference to certainexemplary embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes to the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. It is understood that the drawings are not necessarilyto scale. Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings. Rather, it should be read as consistent withand as support for the following claims which are to have their fullestand fairest scope.

What is claimed is:
 1. An ablation catheter, comprising: an elongatedcatheter body; a distal section distal the catheter body, the distalsection having longitudinal axis and a composite constructioncomprising: a tip electrode; at least one deflectable member and atleast one support member arranged in an alternating sequence along thelongitudinal axis of the distal section, the at least one deflectablemember extending along a first segment of the longitudinal axis of thedistal section proximal of the tip electrode, and the at least onesupport member extending along a second segment of the longitudinal axisof the distal section proximal of the tip electrode, the at least onesupport member being separate from and less flexible than the at leastone deflectable member, each support member carrying a ring electrodeseparate from the tip electrode and a coil sensor on an outer surface ofthe support member.
 2. A catheter of claim 1, the distal sectioncomprising a distal irrigation fluid path extending along thelongitudinal axis of the distal section through the at least onedeflectable member and the at least one support member to deliverirrigation fluid to the respective ring electrode and the tip electrode.3. A catheter of claim 1, the coil sensor being wound around the outersurface of the support member.
 4. A catheter of claim 1, the coil sensorbeing wound in a groove formed in the outer surface of the supportmember.
 5. A catheter of claim 1, the coil sensor being located betweenthe respective ring electrode and the respective support member.
 6. Acatheter of claim 1, the ring electrode being configured to form a gapreservoir between the outer surface of the distal section and an innersurface of the respective support member.
 7. A catheter of claim 6, eachsupport member including an irrigation passage between the distalirrigation fluid path and the gap reservoir.
 8. A catheter of claim 1,the at least one support member having at least one of a lead wirelumen, a puller wire lumen or a sensor cable lumen.
 9. A catheter ofclaim 1, the at least one deflectable member having at least one of alead wire lumen, a puller wire lumen and a sensor cable lumen.
 10. Thecatheter of claim 8, the at least one deflectable member having at leastone of a lead wire lumen, a puller wire lumen and a sensor cable lumen.11. The catheter of claim 2, further comprising an irrigation tubingthat defines the distal irrigation fluid path, the at least onedeflectable member and the at least one support member being supportedon the irrigation tubing.
 12. The catheter of claim 11, each ringelectrode being configured to form a gap reservoir between the outersurface of the respective support member and an inner surface of therespective ring electrode.
 13. The catheter of claim 12, each supportmember including an irrigation passage between the irrigation tubingdefining the distal irrigation fluid path and the gap reservoir.
 14. Thecatheter of claim 12, further comprising openings in the irrigationtubing which communicate with passages in the respective support memberto provide fluid communication between the irrigation tubing and the gapreservoir of the respective ring electrode.
 15. The catheter of claim12, each support member comprising at least one off-axis lumen.
 16. Thecatheter of claim 15, the passages in the respective support memberbeing formed at a predetermined radial angle so that the passages do notinterfere with the at least one off-axis lumen in the respective supportmember.
 17. The catheter of claim 2, the tip electrode including: ashell defining a chamber, the shell having fluid ports; and an internalmember carrying a tip location sensor, the internal member having adiffuser to diffuse fluid entering the chamber via the distal irrigationfluid path.
 18. The catheter of claim 17, the tip location sensor beinggenerally centered in the chamber.